1. Technical Field
The invention relates to an improved system and apparatus for producing bodies for two piece containers. More particularly, the invention relates to a transfer apparatus mounted on the base of a press for reciprocal and linear movement along the base in combination with a pressure sleeve engageable with the can body blanks and formed can bodies which reduces the travel distance of the gripping mechanism of the transfer apparatus to increase the operational speed of the press.
2. Background Information
It is well known in the container forming art to form two piece containers, that is, a container in which the walls and bottom of the container are a one piece member and the top end closure is a separate piece, by stamping a plurality of blanks in a single or double action press from a strip of sheet metal and then subsequently drawing, redrawing, and forming the desired can body configuration into the blank in a series of work stations in the press.
These presses use multiple stage dies, that is, a single downward stroke of the press may simultaneously draw a can body blank into a partially formed can body having a desired shape at a first work station while at another work station in the press the can body will be redrawn into a final configuration or formed with a stepped shoulder or specific profile bottom thereto, with another station then trimming an annular outer flange of the can body to form the final container body configuration.
In these multiple station presses, a transfer mechanism moves the can body blank, the first stage can body and final can body between the work stations. This mechanism usually consists of a pair of gripper bars which are moveable linearly along the press in the direction of travel of the workpieces and can bodies, for transferring the workpieces and can bodies between adjacent work stations. This mechanism also moves perpendicular to this linear direction when gripping the workpieces and can bodies for placing and removing the workpieces at the various work stations for subsequent linear transfer between the work stations. The amount of movement of these grippers perpendicularly toward and away from the travel axis of the workpieces effects the speed of the press since the gripper must retract a sufficient distance to provide clearance for the reciprocal movement of a pressure sleeve or other tooling which is reciprocated by an inner or outer ram of the press. This tooling, and in particular, a pressure sleeve enters a can body blank and holds it in position in an adjacent redraw die cavity of the press at the redraw work station while a concentrically located internal die redraws the blank into a first stage can body. It is desirable to maintain this reciprocal movement of the grippers to a minimum to enable maximum press speed to be obtained while providing secure gripping of the workpiece and subsequently formed can body for moving it linearly along the base of the press in the direction of the press axis.
Recently, various configured containers are being formed from sheet metal other than round containers, such as those having a generally rectangular or elongated oval shaped configurations used for the storage of canned meat products, such as sold under the trademark SPAM® and TREET®. To provide for the secure retention and movement of these elongated can bodies the grippers are formed with a concave recess with curved outer ends, which ends extend partially around the curved corners of the formed can body to securely grip the can body without applying excess pressure to the flexible elongated side walls of the can body. These outwardly extending gripping corners increase the amount of travel of the gripping mechanism toward the retracted position in order to provide clearance from the pressure sleeve, which will be engaged within the can body blank while the transfer mechanism moves linearly along the press to return to a start position for gripping another can body blank. This increased travel reduces the speed of press operation.
Therefore, there is a need for an improved method and apparatus for forming container bodies in a press having a transfer mechanism with grippers which have reduced travel when moving toward a retracted or non-gripping position, to provide clearance from a pressure sleeve while the sleeve is engaged with the can blanks to enable the press to have increased production speed.